Acid sanitizer composition

ABSTRACT

Fatty acid sanitizer concentrates and diluted final solutions are provided which include individual amounts of germicidally effective fatty acid, hydrotrope, strong acid selected from the group consisting of phosphoric and sulphuric acid sufficient to lower the pH of the final solutions to about 1-5, and a concentrate stabilizing weak acid component selected from the group consisting of propionic, butyric and valeric acids and mixtures thereof. The concentrate stabilizing component enhances the room and low temperature phase stability of the concentrates, even when used at very low levels typically ranging from 3.5%-15% by weight. Preferably, the fatty acid is a mixture of nonanoic and decanoic acids, whereas the strong acid is selected from the group consisting of orthophosphoric, sulfuric and mixtures thereof. Alternately, stable concentrates and use dilutions can be provided using undecylenic acid, either alone or in combination with other fatty acids.

RELATED APPLICATION

This is a continuation-in-part of Application Ser. No. 08/131,869, filedOct. 5, 1993, now U.S. Pat. No. 5,330,769, which is a continuation ofapplication Ser. No. 07/973,826, filed Nov. 9, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is broadly concerned with improved fatty acidsanitizer compositions in both concentrate and diluted forms whichinclude a relatively low-cost stabilizing component therein giving thecompositions enhanced stability, particularly at low temperatures. Moreparticularly, the invention is concerned with such concentrates anddiluted solutions which include an effective amount of a weak acidselected from the group consisting of propionic, butyric and valericacids and mixtures thereof; use of such stabilizing components atrelatively moderate levels materially increases the room and lowtemperature stability of the compositions.

2. Description of the Prior Art

A number of different sanitizing compositions have been proposed in thepast for the control of potentially harmful microbial species such asgram-negative and gram-positive bacteria, e.g., E. coli and S. aureus.For example, compositions of this type may be used in the dairy industryfor sanitizing milk-handling equipment and lines. As can be appreciated,such equipment must be routinely cleaned and sanitized to avoid thebuildup of bacteria thereon which would contaminate the milk product.

Representative and effectively equivalent prior sanitizing compositionshave included iodine (U.S. Pat. No. 3,650,965), or fatty acids (U.S.Pat. Nos. 3,867,300 and 4,404,040) as the primary bactericidal agentstherein. Moreover, these compositions are generally sold to end users asconcentrates, and are then diluted with a relatively large fraction ofwater to form final cleaning solutions.

A problem with certain of these prior compositions, and particularly thefatty acid-type sanitizers, stems from the fact that they have poorphase stability unless significant amounts of relatively expensiveadditives (e.g., citric acid) are employed. This in turn means that thecost of the sanitizers is increased, not in order to provide moreeffective germicidal activity, but simply to insure that theconcentrates do not undergo phase separation at room or lowtemperatures.

SUMMARY OF THE INVENTION

The present invention overcomes the problems outlined above, andprovides greatly improved acid sanitizer concentrates and diluted finalsolutions which employ as the stabilizing component thereof relativelyminor amounts of a weak acid selected from the group consisting ofpropionic, butyric and valeric (by which is meant to include bothvaleric and isovaleric) acids and mixtures thereof. These acids are wellknown: propionic (CAS #79-09-04); butyric (CAS #107-92-6); valeric (CAS#109-52-4); isovaleric (CAS #503-74-2).

Broadly speaking, diluted acid sanitizer concentrates in accordance withthe invention include individual amounts of germicidally effective fattyacid, hydrotropesolubilizer, strong acid, a weak acid stabilizingcomponent and water. Generally, the weak acid stabilizing componentshould be present at a level of at least about 2% by weight in theconcentrates, more preferably from about 3.5-15% by weight, and mostpreferably about 10% by weight. In terms of the diluted final solutions,the weak acid stabilizing component should be present at a level of fromabout 30-500 ppm, more preferably from about 40-240 ppm, and mostpreferably about 150-160 ppm. The single most preferred stabilizingcomponent is propionic acid, inasmuch as this component gives the leastoffensive odor. However, excellent stabilizing results can be obtained(with even smaller total quantities of stabilizer) by employing mixturesof the indicated acids, such as propionic and butyric.

The fatty acid component of the concentrates is advantageously selectedfrom the aliphatic C₆ -C₁₁ fatty acids, and particularly nonanoic (CAS#112-05-0) and decanoic (CAS #334-48-5) acids, and mixtures thereof.These fatty acids are normally present at a level of from about 2%-12%by weight depending upon the germicidal activity required in the finaldilute solutions, and most preferably about 6% by weight. Particularlypreferred concentrates contain 3% by weight nonanoic acid and 3% byweight decanoic acid. Again, in the context of the diluted solutions,the fatty acid content thereof should be at least about 50 ppm, morepreferably from about 60-125 ppm, and most preferably about 90-100 ppm.Where the most preferred concentrates are diluted, these dilute finalsolutions should contain about 45-50 ppm nonanoic acid, and about 45-50ppm decanoic acid. In alternative forms, a fatty acid component presentat a level of up to about 3.5% by weight in the concentrate can beprovided, wherein the fatty acid component contains respective minoramounts of decanoic and undecylenic acids.

The hydrotrope component of the compositions can be nonionic or anionicbut is preferably the latter. Surfactants selected from the groupconsisting of the alkane sulfonates (such as alkali metal alkanesulfonates) and the corresponding disulfonates are especially useful.The most preferred anionic hydrotrope is a mixture of sodium 1-octanesulfonate and sodium 1,2-octane disulfonate. In the concentrates, thehydrotrope should be present at a level of from about 5%-20% by weight,more preferably from about 5%-15% by weight and most preferably fromabout 8%-12% by weight; the diluted final solution shouldcorrespondingly contain from about 75-320 ppm, more preferably fromabout 75-235 ppm, and most preferably from about 125-190 ppm hydrotrope.

The strong acid component of the compositions provides the desired lowpH in the final solutions of from about 1-5, and preferably from about2.5-4. The strong acid is advantageously taken from the group consistingof phosphoric, sulfuric and mixtures and thereof, and suitablecompositions can be made using only phosphoric acid, or a combination ofthese two acids. The strong acid is normally present at a level of fromabout 5%-40% by weight in the concentrates, and more preferably fromabout 10%-30% by weight. In the diluted final solutions, the strong acidis present at a level of from about 75-625 ppm, and more preferably fromabout 150-470 ppm.

The balance of the concentrates and final solutions is provided bywater. Thus, in the concentrates, the water content is from about30%-80% by weight, whereas in the final solutions, the water is inexcess of about 99% by weight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The most preferred dilutable acid sanitizer concentrates in accordancewith the invention comprise, and preferably consist essentially of, thefollowing ingredients, wherein all percentages are approximate and on aweight basis:

3% nonanoic acid

3% decanoic acid

8%-10% of a mixture of sodium 1-octane sulfonate and sodium 1,2-octanedisulfonate

8%-30% by weight of strong acid selected from the group consisting oforthophosphoric, sulfuric and mixtures thereof

10% propionic acid

water balance

This preferred concentrate when diluted 1 fluid ounce:6 gallons (1:768)with water gives a final solution adapted for surfacecleaning/sanitizing made up of the following components, wherein allpercentages are approximate and on a weight basis:

47 ppm nonanoic acid

47 ppm decanoic acid

125-160 ppm of a mixture of sodium octane sulfonate and sodium octanedisulfonate

125-470 ppm by weight of strong acid selected from the group consistingof orthophosphoric, sulfuric and mixtures thereof

160 ppm propionic acid

water balance

The above final composition gives excellent microbial activity whencontacted with hard surfaces, and under appropriate time and temperatureconditions, will substantially completely eliminate undesired bacteria.For example, kills greater than 99.999% for both E. coli and S. aureuscan be readily obtained under the standard conditions of AOAC Germicidaland Detergent Sanitizer test described in the Official Methods ofAnalysis of the AOAC, Fourteenth Edition, Ch. 4, Disinfectantsparagraphs 4.020-4.029, incorporated by reference herein.

The presence of strong acid in the compositions serves to lower the pHof final dilute solutions within the range of about 1-5. In thisrespect, the strong acid component is the only material ingredientproviding this degree of pH lowering. That is, the propionic acid hasvirtually no effect upon pH of the final solutions, and hardwater-diluted concentrates with the strong acid component eliminatedhave pHs on the order of 6. Two particularly preferred concentratecompositions in accordance with the invention contain, respectively,about 28% by weight orthophosphoric acid, and a mixture of 8.5% byweight orthophosphoric acid and 9.8% by weight sulfuric acid.

The preferred hydrotrope set forth in the foregoing ingredients can beobtained from commercial sources. For example, the hydrotrope may beobtained from Stepan Chemical Co. as its Bio-Terge PAS-8S product (CAS#5324-84-5). This anionic surfactant is a mixture of sodium 1-octanesulfonate and sodium 1,2-octane disulfonate, and, when used at a levelof 30% by weight in the concentrates of the present invention, providesabout 6%-7.5% by weight of the monosulfonate, and from about 2%-2.5% byweight of the disulfonate. A very similar alkyl sulfonate is also soldby Witco Chemical Co. as "Witconate NAS-8," (CAS #5324-84-5).

EXAMPLE 1

A test was undertaken to determine the effect of use of propionic,butyric and valeric acids in fatty acid hard surface sanitizerconcentrates, insofar as the solubility, homogeneity, and compatibilityof these sanitizers is concerned. In each case, the respective sanitizersamples were prepared in small quantities (10 g, and in some cases 4 g)by simple mixing of the ingredients in 16 mm--125 mm screw cap culturetubes. The ingredients were typically added in the following order:water, strong acid(s), hydrotrope-solubilizer, weak acid(s) and fattyacid(s). In cases where the weak acid was a solid, such as citric acid,it was added first to the water in order to facilitate dissolution. AThermolyne "Maxi Mix II" vortex mixer was used to thoroughly mix theingredients of each sample in a corresponding tube.

The samples were then allowed to stand overnight at normal laboratorytemperature (23° C.-27° C.), and were then observed for any signs ofphase instability such as separation into two or more liquid phases orthe presence of solid precipitate. Samples showing no stability problemsat room temperature were then placed in a refrigerator maintained at atemperature of from about 0° C.-1° C. The samples were then observed,between 24 and 48 hours later, for any signs of phase instability. Thesamples were deemed unstable at low temperature if they did not remainas single phase, homogeneous liquids.

The following tables set forth the compositions tested and the resultsobtained from various fatty acid hard surface sanitizer compositionsmade in accordance with the present invention, and certain conventionalsanitizer compositions. The tables list the ingredients, in units of %by weight, for each test composition, where the balance to 100% of eachsample was water. In these tables, "SEP" refers to separation into twoor more phases, "FR" refers to a totally frozen sample, "PTFR" refers toa partially frozen sample, "SLSH" refers to a slushy sample, "CDS"refers to a sample giving the appearance of curds, and "CRST" refers tothe appearance of crystals in the sample. All of these conditions aredeemed deficient and indicative of failure whereas the "OK" designationindicates an acceptable sample.

                                      TABLE 1                                     __________________________________________________________________________    LOW TEMPERATURE STABILITY                                                     Sample #   1  2  3  4   5  6  7  8  9  10 11 12 13 14 15                      __________________________________________________________________________    98% Octane Sulfonate                                                                     12 12 12 12  12 12 12 12 12 12 12 12 12 12 12                      H.sub.3 PO.sub.4 (75%)                                                                   30 30 30 30  30 30 30 30 30 30 30 30 30 30 30                      Octanoic Acid                                                                            4.8                                                                              4.8                                                                              4.8                                                                              4.8 4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                                                                              4.8                     Decanoic Acid                                                                            3.2                                                                              3.2                                                                              3.2                                                                              3.2 3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                                                                              3.2                     Citric Acid                                                                              22.5                                                                             -- 11.25                                                                              16.875                                                                             -- -- -- -- -- -- -- -- -- --                      Propionic Acid                                                                           -- -- -- --  5  10 -- -- -- -- 3   5.25                                                                            6.5                                                                              -- --                      Butyric Acid                                                                             -- -- -- --  -- -- 5  10 -- -- 3  1.5                                                                              1.5                                                                              -- --                      Valeric Acid                                                                             -- -- -- --  -- -- -- -- 5  10 -- -- -- -- --                      Fumaric Acid                                                                             -- -- -- --  -- -- -- -- -- -- -- -- -- 5  --                      Maleic Acid                                                                              -- -- -- --  -- -- -- -- -- -- -- -- -- -- 20                      R.T. Stability                                                                           OK SEP                                                                              SEP                                                                              OK  OK OK OK OK SEP                                                                              OK OK OK OK SEP                                                                              OK                      0° C. Stability                                                                   OK -- -- SEP SEP                                                                              OK SEP                                                                              OK -- SEP                                                                              SEP                                                                              OK OK -- FR                      __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Sample #   16  17  18  19  20 21  22 23 24 25 26 27                           __________________________________________________________________________    Bioterge PAS-8S                                                                          26.7                                                                              22.9                                                                              20.0                                                                              17.8                                                                              16.0                                                                             8.0 26.7                                                                             22.9                                                                             20.0                                                                             17.8                                                                             16.0                                                                             8.0                          98% Octane Sulfonate                                                                      2.66                                                                              3.98                                                                              5.00                                                                              5.78                                                                              6.40                                                                             9.20                                                                              2.66                                                                             3.98                                                                             5.00                                                                             5.78                                                                             6.40                                                                             9.20                        H.sub.3 P.sub.4 (85%)                                                                    26.5                                                                              26.5                                                                              26.5                                                                              26.5                                                                              26.5                                                                             26.5                                                                              33 33 33 33 33 33                           Octanoic Acid                                                                             6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                             6.5 6.5                                                                              6.5                                                                              6.5                                                                              6.5                                                                              6.5                                                                              6.5                          Decanoic Acid                                                                            3   3   3   3   3  3   3  3  3  3  3  3                            Citric Acid                                                                              20  20  20  20  20 20  -- -- -- -- -- --                           Propionic Acid                                                                           --  --  --  --  -- --  10 10 10 10 10 10                           R.T. Stability                                                                           OK  OK  OK  OK  OK OK  OK OK OK OK OK OK                           0° C. Stability                                                                   SEP FR  FR  FR  FR PTFR                                                                              OK OK OK OK OK OK                           __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Sample #                                                                              28 29 30 31 32 33 34 35  36 37 38 39 40 41 42 43 44 45                __________________________________________________________________________    Bioterge                                                                              35 35 30 30 30 30 30 30  30 30 30 30 30 30 30 30 30 30                PAS-8S                                                                        H.sub.3 PO.sub.4 (85%)                                                                33 33 10 10 33 33 33 33  33 33 33 33 10 10 10 10 10 10                H.sub.2 SO.sub.4 (98%)                                                                -- -- 10 10 -- -- -- --  -- -- -- -- 10 10 10 10 10 10                Decanoic Acid                                                                         2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5 2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5                                                                              2.5               Propionic Acid                                                                        10 15 14 16 16 17.5                                                                             19 15  20    -- -- -- -- -- -- -- --                Acetic Acid                                                                           -- -- -- -- -- -- -- --  -- 20 25 30 -- -- -- -- -- --                Valeric Acid                                                                          -- -- -- -- -- -- -- --  -- -- -- -- 3  4  5  -- -- --                i-Valeric Acid                                                                        -- -- -- -- -- -- -- --  -- -- -- -- -- -- -- 4  5  6                 R. T. Stability                                                                       OK OK OK OK OK OK OK OK  OK OK OK OK OK OK OK OK OK OK                0° C. Stability                                                                FR OK FR OK OK OK OK SLSH                                                                              OK FR FR FR FR OK OK FR OK OK                __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Sample # 46  47  48  49  50  51  52  53  54  55                               __________________________________________________________________________    BiotergePAS-8S                                                                         30  35  30  40  30  30  40  30  30  35                               H.sub.3 PO.sub.4 (85%)                                                                   26.5                                                                              26.5                                                                              26.5                                                                              26.5                                                                              26.5                                                                            10  10  10  10  10                               H.sub.2 SO.sub.4 (98%)                                                                 --  --  --  --  --  10  10  10  10  10                               Octanoic Acid                                                                            6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                            Decanoic Acid                                                                           3   3   3   3   3   3   3   3   3   3                               Citric Acid                                                                            20  20  10  20  20  20  20  --  --  --                               Propionic Acid                                                                         --  --  --  --  --  --  --   5  10   5                               R. T. Stability                                                                        SEP OK  SEP OK  SEP SEP OK  OK  OK  OK                               0° C. Stability                                                                 --  FR  --  FR  --  --  SEP OK  OK  OK                               __________________________________________________________________________    Sample # 56  57  58  59  60  61  62  63  64  65                               __________________________________________________________________________    BiotergePAS-8S                                                                         40  45  50  40  40  30  30  30  35  35                               H.sub.3 PO.sub.4 (85%)                                                                 10  10  10  33  33  33  33  33  33  33                               H.sub.2 SO.sub.4 (98%)                                                                 10  10  10  --  --  --  --  --  --  --                               Octanoic Acid                                                                            6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                                                                               6.5                            Decanoic Acid                                                                           3   3   3   3   3   3   3   3   3   3                               Citric Acid                                                                            --  --  --  --  --  --  --  --  --  --                               Propionic Acid                                                                          5   5   5  10  15   5  10  15   5  10                               R. T. Stability                                                                        OK  OK  OK  OK  OK  OK  OK  OK  OK  OK                               0° C. Stability                                                                 OK  OK  OK  CDS OK  OK  OK  SEP CDS CDS                              __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    Sample # 66 67 68  69 70 71 72 73 74                                          __________________________________________________________________________    BiotergePAS-8S                                                                         30 35 35  35 35 30 30 30 30                                          H.sub.3 PO.sub.4 (85%)                                                                 30 30 30  30 30 10 10 33 33                                          H.sub.2 SO.sub.4 (98%)                                                                 -- -- --  -- -- 10 10 -- --                                          Nonanoic Acid                                                                           3  3  3   3  3  3  3  3  3                                          Decanoic Acid                                                                           3  3  3   3  3  3  3  3  3                                          Citric Acid                                                                            20 20 20  20 15  5 10  5 10                                          Propionic Acid                                                                          5  5   7.5                                                                              9 10 -- -- -- --                                          R.T. Stability                                                                         SEP                                                                              OK OK  OK OK OK OK OK OK                                          0° C. Stability                                                                 -- FR SEP SEP                                                                              SEP                                                                              FR FR FR FR                                          __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Sample # 75 76 77 78 79  80  81 82 83 84                                      __________________________________________________________________________    BiotergePAS-8S                                                                         30 30 30 30 30  30  30 30 30 30                                      H.sub.3 PO.sub.4 (85%)                                                                 33 33 33 10 10  10  10 10 33 33                                      H.sub.2 SO.sub.4 (98%)                                                                 -- -- -- 10 10  10  10 10 -- --                                      Nonanoic Acid                                                                           3  3  3  3  3   3   3  3  3  3                                      Decanoic Acid                                                                           3  3  3  3  3   3   3  3  3  3                                      Acetic Acid                                                                             5 10 15  5 10  15  -- -- -- --                                      Propionic Acid                                                                         -- -- -- -- --  --  10  5  5 10                                      R.T. Stability                                                                         OK OK OK OK OK  OK  OK OK OK OK                                      0° C. Stability                                                                 FR FR FR FR SLSH                                                                              SLSH                                                                              OK FR FR OK                                      __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________    Sample # 85  86  87 88  89  90 91  92  93  94 95  96                          __________________________________________________________________________    BiotergePAS-8S                                                                         30  30  30 30  30  30 30  30  30  30 30  30                          H.sub.3 PO.sub.4 (85%)                                                                 10  10  33 33  10  33 10  33  10  10 10  10                          H.sub.2 SO.sub.4 (98%)                                                                 10  10  -- --  10  -- 10  --  10  10 10  10                          Nonanoic Acid                                                                           3   3   3  3   3   3  3   3   3   3  3   3                          Decanoic Acid                                                                           3   3   3  3   3   3  3   3   3   3  3   3                          Propionic Acid                                                                         --  --  -- --  --   5  5    2.5                                                                               2.5                                                                              3 --  --                          Butyric Acid                                                                             2.5                                                                              5   5   2.5                                                                              1   1  1   1   1   1     --                          Valeric Acid                                                                           --  --  -- --  --  -- --  --  --  --   2.5                                                                              5                          i-Valeric Acid                                                                         --  --  -- --  --  -- --  --  --  -- --  --                          Hexanoic Acid                                                                          --  --  -- --  --  -- --  --  --  -- --  --                          Heptanoic Acid                                                                         --  --  -- --  --  -- --  --  --  -- --  --                          R.T. Stability                                                                         OK  OK  OK OK  OK  OK OK  OK  OK  OK OK  SEP                         0° C. Stability                                                                 OK  OK  OK SEP SLSH                                                                              OK OK  OK  CRST                                                                              OK SEP --                          __________________________________________________________________________    Sample # 97  98  99 100 101 102                                                                              103 104 105 106                                                                              107 108                         __________________________________________________________________________    BiotergePAS-8S                                                                         30  30  30 30  30  30 30  30  30  30 30  30                          H.sub.3 PO.sub.4 (85%)                                                                 33  33  33 33  33  10 10  10  33  33 33  33                          H.sub.2 SO.sub.4 (98%)                                                                 --  --  -- --  --  10 10  10  --  -- --  --                          Nonanoic Acid                                                                           3   3   3  3   3   3  3   3   3   3  3   3                          Decanoic Acid                                                                           3   3   3  3   3   3  3   3   3   3  3   3                          Propionic Acid                                                                         --  --  -- --   3  -- --   3  --  -- --  --                          Butyric Acid                                                                           --  --  -- --  --  -- --  --  --  -- --  --                          Valeric Acid                                                                            5    2.5  --  --  -- --  --  --  -- --  --                          i-Valeric Acid                                                                         --  --   1   2.5                                                                              1   1   2.5                                                                              1  --  -- --  --                          Hexanoic Acid                                                                          --  --  -- --  --  -- --  --    2.5                                                                              5 --  --                          Heptanoic Acid                                                                         --  --  -- --  --  -- --  --  --  --   2.5                                                                              5                          R.T. Stability                                                                         OK  OK  SEP                                                                              OK  OK  OK OK  OK  SEP SEP                                                                              SEP SEP                         0° C. Stability                                                                 OK  SEP -- SEP CRST                                                                              SEP                                                                              SEP OK  --  -- --  --                          __________________________________________________________________________

Referring first to Table 1, it can be seen that a sanitizer containing4.8% by weight octanoic acid and 3.2% by weight decanoic acid hasappropriate stability if a large amount (22.5% by weight) citric acid isemployed. However, elimination of the citric acid or reduction in theamounts thereof, yields unstable sanitizers (samples #1-4). This is tobe contrasted with samples #6 and 8, wherein 10% by weight of propionicor butyric acid gives a stable system. Thus, less than half the amountof the acids of the invention can be used, in lieu of the amount ofcitric acid needed. The total amount of weak acids can be even furtherlowered by using a combination of propionic and butyric acids (samples#12-13). Finally, fumaric and maleic acids were shown to be ineffectiveas system stabilizers (samples #14-15).

Table 2 (6.5% octanoic/3% decanoic acid samples) demonstrates that useof 20% citric acid is ineffective in achieving stable compositions, evenwhen varying amounts of the mono and disulfonate are used (samples#16-21). However, comparative samples #22-27 each containing 10% byweight propionic acid, are stable. This further confirms thatsignificantly more citric acid is required, as compared with the acidsof the invention. This represents a significant commercial advantage inthat the present-day price of citric acid is approximately $.80 perpound whereas the price for propionic acid is presently about $.40 perpound.

Table 3 (2.5% decanoic acid samples) represents another series of testsand demonstrates that compositions can be made using a combination ofstrong acids, in this case phosphoric and sulfuric; and that suchcompositions can be stabilized with appropriate amounts of the acids ofthe invention. For example, sample #41 demonstrates that a very minoramount of valeric acid (4% by weight) can be used to good effect.Similarly, small amounts of isovaleric acid (i-valeric acid) are alsoeffective (samples #44-45). Finally, as depicted with samples #37-39,even significant amounts of acetic acid failed to give a stablecomposition.

Table 4 (6.5% octanoic/3% decanoic acid samples) provides furtherconfirming evidence and shows that with this system, 5% by weightpropionic acid is more effective than 20% by weight citric acid (samples#53, 55-58 and 61 versus samples #46-52).

All of the samples of Table 5 (all samples of Tables 5-7 had 3%nonanoic/3% decanoic fatty acids therein) failed, inasmuch as all thesesamples contained from between 5%-20% by weight citric acid. Thesefailures resulted even though from 5%-10% by weight propionic acid wasused in combination with the citric acid. This establishes that thepropionic acid functions in a superior manner as compared with citricacid, and the two are not additive in effect.

Table 6 illustrates that in compositions containing a mixture ofnonanoic and decanoic acids as the fatty acid component, acetic acid isineffective, but that 10% by weight of propionic acid therein givesstable systems (samples #75-80 versus samples #81 and 84).

Table 7 records the results from a series of tests using variouscombinations of strong acid and weak acids, and confirms that arelatively small amount of butyric acid (2.5% by weight) gives a stableproduct (sample #85) and that a combination of 2.5% by weight propionicacid and 1% by weight butyric acid also gives a stable system (sample#92).

EXAMPLE 2

A preferred concentrate in accordance with the invention (sample #81,Table 6) was tested to determine the amount of foam generated in alaboratory test. The concentrate was diluted at a ratio of 1 fluid ounceconcentrate per 6 gallons of 500 ppm AOAC synthetic hard water toprovide a final dilute solution. The dilute solution was then tested intriplicate as set forth below.

Specifically, 300 milliliters of the dilute solution (at roomtemperature) was placed in a conventional, upright, open-top, 1000milliliter graduated cylinder. A spherical alumina sparging device(AX536, Norton Co., Industrial Ceramics Div., Worcester, Mass.), soakedat least 4 hours in the dilute solution, was used for foam generation.This sparger is specified in a standard dynamic foam test (ASTM#D892-89), and was attached to a line connected with a source ofpressurized gas (nitrogen). The sparger with tubing attached was loweredinto the solution in the graduated cylinder, and seated adjacent thebottom of the latter. The flow of gas through the line and sparger wasadjusted to a rate of 2 liter/min., and was then allowed to pass intothe solution for a period of 15 seconds. At the end of the 15 secondperiod, the total amount of foam present in the cylinder was measured bynoting the uppermost foam level and subtracting therefrom the bottomlevel of the foam. The following results were recorded:

    ______________________________________                                                Upper Foam   Bottom Foam                                                                              Total Foam                                    Run #   Level (ml)   Level (ml) (ml)                                          ______________________________________                                        1       610          100        510                                           2       610          80         530                                           3       610          80         530                                           ______________________________________                                    

EXAMPLE 3

In this Example, stable compositions making use of C₁₁ fatty acid(undecylenic) are illustrated. The compositions were prepared as setforth in Example 1, and included the following ingredients on a percentby weight basis. The compositions were also tested for room temperatureand 0° C. stability, these results are set forth below:

                  TABLE 8                                                         ______________________________________                                        Sample #            109     110                                               ______________________________________                                        BioTerge PS-8S      30      30                                                Phosphoric Acid (85%)                                                                             33      33                                                Decanoic Acid         2.0     1.5                                             Undecylenic Acid      1.5     2.0                                             Propionic Acid      10      10                                                Water                 23.5    23.5                                            R.T. Stability      OK      OK                                                0° Stability OK      OK                                                ______________________________________                                    

EXAMPLE 4

The following Example demonstrates that nonionic surfactants (IgepalCO-887, Pluronic P-85 and Pluronic P-65 ) can be used to produce acidsanitizers in accordance with the invention. These compositions wereprepared as set forth in Example 1 and included the followingingredients on a percent by weight basis. The compositions hadacceptable room temperature stabilities.

                  TABLE 9                                                         ______________________________________                                        Sample #             111    112                                               ______________________________________                                        Igepal CO-887        15     --                                                Pluronic P-85        --     10                                                Pluronic P-65        --     10                                                Sulfuric Acid (96%)  10     10                                                Phosphoric Acid (85%)                                                                              10     10                                                Propionic Acid       10     10                                                Decanoic Acid         3      3                                                Nonanoic Acid         3      3                                                Water                49     44                                                ______________________________________                                    

We claim:
 1. An aqueous, dilutable acid sanitizer concentratecomposition comprising individual amounts of water, from about 2-12% byweight of an aliphatic C₆ -C₁₁ germicidally effective fatty acid, fromabout 5-20% by weight of hydrotrope-solubilizer selected from the groupconsisting of nonionic and anionic hydrotrope-solubilizers, from about5-40% by weight of a strong acid selected from the group consisting ofphosphoric and sulfuric acids and mixtures thereof, and a component forgiving the composition enhanced stability, said stabilizing componentcomprising an effective amount of from about 3.5-15% by weight of a weakacid selected from the group consisting of propionic, butyric andvaleric acids and mixtures thereof, said composition, when diluted inwater to form a use solution having a pH of from about 1-5.
 2. Thecomposition of claim 1, said stabilizing component being present at alevel of about 10% by weight.
 3. The composition of claim 1, saidstabilizing component being propionic acid.
 4. The composition of claim1, said stabilizing component being a mixture of said acids.
 5. Thecomposition of claim 1, said fatty acid being selected from the groupconsisting of nonanoic, decanoic, undecylenic fatty acids and mixturesthereof.
 6. The composition of claim 1, said fatty acid being present ata level of about 6% by weight.
 7. The composition of claim 1, saidhydrotrope-solubilizer comprising sodium 1-octane sulfonate and sodium1,2-octane disulfonate.
 8. The composition of claim 1, said level ofhydrotrope-solubilizer being from about 5%-15% by weight.
 9. Thecomposition of claim 1, said strong acid being phosphoric acid.
 10. Thecomposition of claim 1, said strong acid being a mixture of phosphoricand sulfuric acid.
 11. The composition of claim 1, said strong acidcomprising about 8.5% by weight orthophosphoric acid and about 9.8% byweight sulfuric acid.
 12. The composition of claim 1, said acidcomprising about 28% by weight orthophosphoric acid.
 13. The compositionof claim 1, said hydrotrope-solubilizer being selected from the groupconsisting of the alkane sulfonates and disulfonates.
 14. A dilutableacid sanitizer concentrate composition comprising:about 3.5% by weightof a fatty acid component comprising respective amounts of decanoic acidand undecylenic acid; from about 8-10% by weight of a mixture of sodiumoctane sulfonate and sodium octane disulfonate; from about 8-30% byweight of a strong acid selected from the group consisting oforthophosphoric, sulfuric and mixtures thereof; a component for givingthe composition enhanced stability and comprising about 10% by weight ofpropionic acid; and the balance of said composition up to 100% by weightbeing water.
 15. A dilutable acid sanitizer concentrate compositionconsisting essentially of:about 3.5% by weight of a fatty acid componentcomprising respective amounts of decanoic acid and undecylenic acid;from about 8-10% by weight of a mixture of sodium octane sulfonate andsodium octane disulfonate; from about 8-30% by weight of a strong acidselected from the group consisting of orthophosphoric, sulfuric andmixtures thereof; a component for giving the composition enhancedstability and comprising about 10% by weight of propionic acid; and thebalance of said composition up to 100% by weight being water.